Peotection of axtebnating-ctjbrent-distbibtjting cibcuits



Apr. 3, 1923. 1,450,425. R. v. BINGAY.

PROTECTION OF ALTERNATING CURRENT DISTRIBUTING CIRCUITS.

FILED OCT. I7| I9I9.

Patented Apr. 3, 1923.

UNITED STATES PATENT OFFICE.

ROBERT V. BINGAY, F PITTSBURGH. PENNSYLVANIA, ASSIGNOR TO PITTSBURGH TRANSFORMER COMPANY, A CORPORATION OF PENNSYLVANIA.

PROTECTION OF ALTERNATING-CUBRENT-DISTRIBUTING CIRCUITS.

Application filed October 17, [919.

To all whom it may concern:

Be it known that I, Roaenr V. Bmcn'. a citizen of the United States, residing at Pittsburgh, in the county of Alleghenty and State of Pennsylvania, have invente certain new and useful Improvements in Protection of Alternating-Current-Distributin Circuits, of which the following is a specification.

My invention relates to the protection of alternating current circuits and apparatus, and particularly to the protection of the low tension or distributing circuits and to the apparatus supplied thereby where the source 16 is of hi h tension and where the reduction of the big voltage to the low voltage of dis tribution is by means of transformers or other apparatus It sometimes happens that the insulation 20 between the'high tension circuitsor high tension coils of the transforming apparatus and the low tension coils or low tension-circuits, breaks down so that some point of the low tension side is electrically connected to some point of the high tension side. This may occur from various causes such as a breakdown of the insulation directly between the high tension and low tension coils of the step-down transformer, or the connection between the high and low tension coils may occur indirectly between the coils through the iron core or iron casing of the transformer, or between the leads directly or indirectly. In such an event, the high potential of the high tension system is superimposed upon the low tension portion of the system. With such a condition the low tension portion of the system is correspondingly subjected to the potential of the point of break-down in the high tension side of the system, and this may be extremely high and very much exceed the potential intended to be imposed upon the secondary portion or portions of the system. This condition imposes upon the secondary circuit such an abnormally high potential that it becomes a source of danger to users and to the various apparatus connected to the distribution system. It also becomes a menace to other property and greatly increases the fire hazard. With the two-wire distributing circuits, there is no normal neutral point available for grounding and attempts to secure protectioii by grounding one side or the other of the twn'wire distributing means Serial No. 113L322.

have proven unsatisfactory. in accordance with my invention. however, i introduce means connected between the t vo-\\'ire low tension distributing mains for the purpose of providing a neutral point, which point is in turn connected to the ground. By this means, the system is not in any way unbalanced and by reason of this ground connection to a created neutral point, the potential to which any point in the secondary distributing system may be raised above or below that of the earth, is restricted to a fixed amount, which would be less than might occur without the ground connection. Furthermore, the low tension circuits and the apparatus connected therewith are relieved from high electro-static charges by reason of my improved form and location of ground connection, which relieves the circuits and apparatus from high potential strains which might otherwise occur, and which would sub ject such circuits and apparatus to the liability of break-down of their insulation. Again the provision of my improved ground connection will, in the case of abnormal connection between the high tension and low tension portions of the system as above referred to, result in some cases in the immediate 0 ning of the circuit breakers and fuses or 0t er protective apparatus caused by the sudden and abnormal fiow of current, so as to entirely disconnect the secondary distributing circuit from the source and so prevent danger to persons and to property which otherwise might occur.

My invention will be understood by referring to the accompanying drawing which is a diagram illustrating my invention.

A source of alternatin current is indicated at 1 which may be of very high tension so as to supply the high tension mains directl or the source may be of comparatively ibw tension and a step-up transformer 2 may be utilized for supplying the high tension constant potential transmission mains 3. Step-down transformers are indicated at 4 and 5 located at desired points for supplying the low tension constant potential two wire distributing circuits 6, 7. Reactancc coils are indicated at 8, 9 each having an iron core 10. ll. Leads l2. [3 extend from terminals or taps from the coils 8, 9 connecting these coils in circuit across the two-wire distributing mains. .-\t the. middle point of each coil an electrical connection is made to ground, which ground connection is represented at G. The reactance coils and the core will be suitably proportioned so as to absorb but a small amount of energy from the circuits and in order to adapt or adjust the reactance coils to circuits of difl'crcnt voltages I have shown the reactance coils as being provided with taps near their ends to which the leads from the distributing cirunits may be connected as required by the particular conditions.

It will be apparent that the reactant-e coils provide a neutral point at a position in the coil midway between the points of the coils which are connected respectively to the two wires of the distributing circuits and that by making a ground connection to this neutral point as indicated in the drawing. the secondary circuits are suitably grounded in a balanced manner affording the protection above referred to with the attendant advantages. For instance in case of a high tension ground as G and a failure of the insulation between the high tension circuit and low tension circuit 7 as at S, were it not for the shunt provided by the reactance coil 9 and the ground at G, the full high tension voltage would be impressed between the wires of the low tension circuit and the ground, as G". Such a voltage would be destructive in the low tension system burning out apparatus and instruments that hap' pened to be grounded and endangering the ives of persons comin between the wires and grounded parts. fn the system shown excessive current through the coil 9 due to connection with the high tension line may act to disconnect the secondary as by operating the usual protective switches in the circuit and thus afford further protection.

My invention is susceptible of embodiment in various forms without departing from the scope thereof, and is also capable of being applied at any desired point or points in the distributing system.

Having thus described my invention, what I declare as new and desire to secure by Lettcrs Patent of the United States is l. In an alternating current system the combination with a high tension source, of a low tension two-wire distributing circuit, means for transforming energy of the high tension source to the low tension of the distributing circuit, a reactance coil connected across the wires of said distributing circuit, and a ground connection from approximately the neutral point of said reactance coil protecting said low tension circuit against the voltage of the high tension circult.

L. In an alternating current system the combination with a high tension source, of a low tension two-wire distributing circuit, means for transforming energy of the-hi h tension source to the low tension of the d18- tributing circuit, a. reactance coil connected across the two-wires of said distributin' circuit and having a plurality of taps, an a ground connection to a point at a potential approximately midway between the potentials of the two wires of saiddista'ibuting circuit protecting said low tension circuit against the voltage of the high tension cir cult.

3. In an alternating current system the combination with a transformer having l1 nected across the terminalsof the low tension coil, and a ground connection from ap proximately the neutral oint of the reactance coil protectin the ow tension circuit against excess of v0 ta'ge frorn'the high tens1on circuit. i

ROBERT v. BIN AX.

e and low tension co1ls,- of a reactancewcon- 1-- 

